Digit tube with the characters secured only at one end



Oct. 14, 1969 A. A. M. HENDRIKS ET AL 3,473,068

DIGIT TUBE WITH THE CHARACTERS SECURED ONLY AT ONE END Filed Oct. 19. 1967 2 Sheets-Sheet 1 27 29 n 2 35M: AW: 5 .1 20

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DIGIT TUBE WITH THE CHARACTERS SECURED ONLY AT ONE END Filed Oct. 19. 1967 2 Sheets-Sheet 2 RUS w SASbEZS BY E, N S MW United States Patent M US. Cl. 313-1095 8 Claims ABSTRACT OF THE DISCLOSURE A gas-filled character display tube the individual character shaped electrodes of which are secured at one end directly to connection pins which extend through the tube base.

The invention relates to a character display tube having a number of electrodes in the form of characters arranged one behind the other and in particular to such a tube in which the characters are secured in the tube only on one side. The invention relates to a method of manufacturing such a tube.

In such tubes, the electrodes which may have the form of characters, for example, letters or digits, are generally arranged one behind the other and are supported in the tube by one or two pins through which the electrodes are threaded and separated by insulating spacing rings. This threading is a time-consuming job which may be avoided if the characters are clamped between individual insulating frames, the frames being stacked. In the known construction separate connection conductors, or connection conductors which form one assembly with the characters, must always be arranged between the characters and the current supply pins which likewise is time-consuming.

According to the invention a very simple assembly is obtained if in a tube having characters whihc are arranged one behind the other and are supported in the tube only on one side, each character is secured directly and mainly parallel to a current supply pin sealed in the base of the tube and is supported by said pin. The connection is preferably carried out by welding, in particular by stud-welding at the end of the pin. For that purpose it will generally be necessary to bend the pins somewhat previously, the pins being sealed in the base of the tube according to a given pattern, so that the place of the end of each pin corresponds to the place of the characters to be secured thereto. This bending may be carried out mechanically in a simple manner. The electrodes in the form of characters are successively welded on the supply pins one behind the other for which purpose they are held by means of tongs which may also be connected to one terminal of a Welding apparatus. The other terminal is connected to a holder in which the contact pins of the base of the tube are inserted. At least one part of the jaw of the tongs with which the characters are held must have a thickness which is equal to, or smaller than, the distance between the characters so that this part can be slid between the held character and the character already connected previously.

The characters are individually welded one after the other on the associated current supply pin, preferably by stud welding on the end of the pin. These manipulations can be preformed simply and automatically.

Because the characters are secured only on one side in the tube they must be manufactured from comparatively strong material. For this purpose, a chromium-nickel-iron Patented Oct. 14, 1969 ICC alloy is preferred while the width of the material of the characters on the side of the connection may be somewhat larger than on the upper side.

The contact pins also preferably consist of a chromiumnickel-iron alloy since this can be readily sealed in glass. The advantage of welding the characters to the pins as compared with, for example, soldering is that for soldering the chromium-containing parts first have to be silver plated at the places to be soldered since chromium-containing materials cannot be soldered as such. Welding on the contrary can be done without difliculty.

The invention will be described with reference to the accompanying drawing, in which:

FIG. 1 is a side elevation of an electrode system of a character display tube according to the invention mounted on a base of a tube,

FIG. 2 is a plan view of FIG 1, and

FIG. 3 is a side elevation of such a tube.

In the figures 17 denotes a glass base part in which the pins 1 to 16 are sealed according to a pattern which mainly consists of four rows. The pins are bent at one end in such manner that the electrodes, or other parts, can be directly secured to the pins. Subsequently a mica centering plate 19 is slid onto the pins followed by a metal plate 20 in which apertures 28 are provided which are larger than the diameters of the pins 1 to 16 so that the pins extend through plate 20 in an insulated manner. The plate 20 comprises parts 27 which are forced through, so that this plate remains at some distance from the mica plate 19. As a result of this, leakage between the pins by the deposition of metal particles on the mica plate is avoided. Such a leakage would cause several characters to luminesce simultaneously.

Digits 1'0' consisting of chromium-nickel steel alloy are welded onto the pins 1-10. Since the pins themselves likewise consist of such an alloy welding presents no difficulties. The screening plate 20 preferably consists of iron which is covered with a black layer. The length of the pins 13 to 16 is chosen to be such that the upper ends of said pins engage the mica plate 19. The pins 11 and 14 extend through the plates 19 to 20 and are secured to the metal plate 20 by means of angle pieces 26. Plates 19 and 20 are enclosed between the ends of the pins 13 and 16 and the angle pieces 26.

The pin 12 and/or 15 may project a. little above the plate 20 and be provided with a decimal character 25 (period or comma). If this character consists of a metal having a lower-function than chromium-nickel steel, for example, pure iron or molybdenum, the advantage is obtained that as a result of the lower work function thereof with respect to the chromium-nickel steel of the other characters, a significant glow discharge on the decimal character 25 occurs, in spite of the small surface, without it "being necessary that the voltage thereof be higher than of the other characters having a comparatively large surface. This is otherwise found to be necessary since an electrode having a small surface area is screened too much by the large electrodes to be covered with a sufficiently significant glow light at the same voltage.

After welding the digits to the pins the anode cage consisting of a plate-shaped part 21 and a perforated part 22 is arranged around the electrode system and welded to the screening plate 20. The anode 21 comprises a mercury holder in the form of a glass tube 23 containing a drop of mercury. The tube 23 is secured in a plate-shaped holder 24, which can be heated by high-frequency currents, or by radiation from a heat source, as a result of which first the glass tube is softened and then bursts after which the mercury evaporates.

This construction of the holder has the advantage with respect to a construction in which the mercury-containing glass tube is heated by means of a filament wire wound around the tube, that no additional contact pin for the filament current is necessary and that no current supply conductors to the filament are necessary which have to be surrounded with insulating tubes to prevent the conductors from luminescing. A holder with a filament in gasfilled tubes rnust consequently always be arranged near to the base of the tube which has the disadvantage that mercury may deposit on the base and the mica centering plate and cause leakage between the electrodes.

Because in the above-described tube, a sheet metal holder is arranged around the glass tube which can be heated by means of high-frequency currents or by radiation from a heat source, the holder may be arranged without objection above the electrode system so that deposition of mercury at undesired places can be avoided. It has been found that as a result of the heating, the glass softens externally and bursts locally before the mercury pressure has become so high, that the whole tube explodes. The softened glass in addition readily adheres to the metal holder so that no separate glass particles are produced in the tube.

Subsequently the envelope 18 is sealed to the base part 17 after which the tube is evacuated, provided with a suitable gas filling, and sealed.

The welding of the electrodes 1' to to the pins 1 to may preferably be effected by means of a stud weld on top of the ends of the pins. The advantage thereof is that the end faces of the pins which are coated with an insulating layer are always uncovered as a result of the cutting, so that the local removal of the insulating layer is not necessary. For stud welding, for example, first the character 6 is held in tongs which are connected to a terminal of the welding apparatus. The base part 17 is placed in a holder as a result of which the pins can be connected to the other terminal of the welding apparatus. After welding the character 6' to the pin 6, the characters 5, 7, 4, 8', 3', 9, 2', 0, and 1' are successively welded to the associated pins in the same manner. The welding tongs must consequently have jaws of which at least one of the parts has a thickness which is smaller than or equal to the distance between two characters so that this part of the tongs can be moved between the characters to be welded and the character already welded previously. If care is taken that the welding current cannot flow also to the previously welded character, this part of the jaws of the welding tongs may also serve as a spacing member for the character during provision and welding thereof.

The pin with the part 29 projects a little above the screening plate and the cathode voltage is applied by means of a high-value resistor. The resistance is so high that the end 29 of the pin 15 substantially show-s no glowlight, but operates only as an activator for the pre-ionization of the gas as a result of which the ignition speed of the characters is increased.

The anode cage 21, 22 and the screening plate 20 are blackened entirely so that they form a dark background and enable a clear reading. The screening plate 20 also causes an even distribution of the anode field so that no additional anode characters or anodes are necessary. The characters may be digits or letters and the like. Because they consist of chromium-nickel steel, they have a sufli cient rigidity so that it is necessary that they be secured only on one side, the lower side. The width of the material of the characters at the lower side may be somewhat larger than at the upper side in order to increase their rigidity. For shock-resistant arrangements the characters may be provided, if desired, with lugs at the upper ends, which lugs may be secured in an insulating rod so that the characters form a rigid unit. The insulating rod thus only serves to connect the characters together and not to secure and support the characters in the tube.

Although a particular embodiment has been described, the invention may also be carried into effect in different manners. For example, the electrodes may be connected to the supply pins by soldering or by clamping.

Therefore, while the invention has been described with reference to a particular embodiment thereof, other modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. A character-display tube having an anode, a plurality of character-shaped cathode electrodes spaced from said anode and arranged directly one behind the other without other intervening electrodes and supporting elements therebetween, said cathode electrodes being secured and supported only at one end in the tube, each charactershaped electrode consisting of a chromium nickel alloy, each of said electrodes being secured directly and substantially mainly parallel to a current supply pin sealed in the base of the tube and being supported by said pin, the width of each of said electrodes adjacent the current supply pin being larger than the end remote from the pin.

2. A character-display tube as claimed in claim 1 in which each character is stud-welded to the end of a current supply pin.

3. A character-display tube as claimed in claiam 1 in which one of the character-shaped electrodes has a surface area substantially smaller than that of any other electrode, said electrode consisting of a material of lower work-function than the material of the remaining electrodes whereby with the same potential applied to that electrode as to the other electrodes, a significant glowdischarge occurs.

4. A character-display tube as claimed in claim 1 in which the end of a current supply pin extends into the discharge space and serves as a pre-ionization electrode.

5. A character-display tube as claimed in claim 1 in which a glass tube containing a drop of mercury in a sheet metal holder is secured to an anode on the side of the electrodes remote from the base.

6. A character-display tube as claimed in claim 1 in which the anode surrounds the character-shaped electrodes and comprises a plate-shaped portion and a perforated portion.

7. A character-display tube as claimed in claim 6 in which the anode is blackened to provide a dark background for the electrodes.

8. A character-display tube as claimed in claim 3 in which the material of lower work function is molybdenum.

References Cited UNITED STATES PATENTS 2,578,370 12/1951 Peck 313-198 2,618,760 11/1952 Hancock et al. 313-1095 2,756,366 7/1956 Maynard 313-1095 X 2,991,387 7/1961 McCauley 313-1095 2,991,388 7/1961 Wightman 313-1095 3,136,911 6/1964 Crawford et al. 313-109.5 3,318,649 5/1967 Keller et al. 313-1095 X 3,358,176 12/1967 Rosenberg et a1. 313-1095 JAMES W. LAWRENCE, Primary Examiner DAVID OREILLY, Assistant Examiner 

